Bug 742361 - GCC 4.7 mingw fails to compile cairo due to missing ffs declaration r=jrmuizel

gfx/cairo/cairo/src/cairo-compiler-private.h

@@ -234,6 +234,10 @@ ffs (int x)
 }
 #endif
 
+#elif defined(__WIN32__) && defined(__GNUC__)
+
+#define ffs(x) __builtin_ffs(x)
+
 #endif
 
 #if defined(_MSC_VER) && defined(_M_IX86)

gfx/cairo/win32-ffs-gcc.patch

@@ -0,0 +1,25 @@
+diff --git a/gfx/cairo/cairo/src/cairo-compiler-private.h b/gfx/cairo/cairo/src/cairo-compiler-private.h
+index ffac9ce..9a05831 100644
+--- a/gfx/cairo/cairo/src/cairo-compiler-private.h
++++ b/gfx/cairo/cairo/src/cairo-compiler-private.h
+@@ -229,16 +229,20 @@ ffs (int x)
+ 
+     if (_BitScanForward(&i, x) != 0)
+ 	return i + 1;
+ 
+     return 0;
+ }
+ #endif
+ 
++#elif defined(__WIN32__) && defined(__GNUC__)
++
++#define ffs(x) __builtin_ffs(x)
++
+ #endif
+ 
+ #if defined(_MSC_VER) && defined(_M_IX86)
+ /* When compiling with /Gy and /OPT:ICF identical functions will be folded in together.
+    The CAIRO_ENSURE_UNIQUE macro ensures that a function is always unique and
+    will never be folded into another one. Something like this might eventually
+    be needed for GCC but it seems fine for now. */
+ #define CAIRO_ENSURE_UNIQUE                       \